1. Field of the Invention
The present invention relates generally to an apparatus and method for multimedia services, and more particularly, to an apparatus and method for ensuring service quality for multimedia services.
2. Description of the Related Art
Many efforts are currently being made to improve service quality of multimedia services in a dynamic wireless environment.
Generally, in order to provide multimedia services with improved quality in a dynamic wireless environment, various plans to efficiently cope with changes in time/space-varying channel are required.
As an example of these plans, when a multimedia service is provided in a dynamic wireless environment, signal strength of each region is measured, and an appropriate bit rate is supported for each region based on the measured signal strength. In this case, however, changes in channel environment are not considered, which makes it difficult to guarantee a reliable service quality of the multimedia services. For example, if a channel environment less than a representation of a lowest bit rate for a multimedia service lasts for at least a specific time (e.g., min_Buffer Time, MPD[ ]), underflow may occur in a buffer of a server providing the multimedia service.
Conventionally, in a dynamic wireless environment, the following three plans are used to minimize degradation of service quality caused by underflow.
A first plan, i.e., a ‘prepare to low-bit rate representation’ plan, prepares for a representation requiring a low bit rate having a possibility of underflow, thereby minimizing a quality degradation caused by the underflow. However, this plan may cause overhead when preparing for and managing an additional representation.
A second plan, i.e., a ‘moof skip’ plan, minimizes underflow by skipping on a data frame (or movie fragment (moof) box) basis depending on control information provided from a media data box (mdat) for multimedia services without preparation for additional representation. However, this second plan may increase in play-out discontinuity due to the skip on a moof basis.
A third plan, i.e., an ‘initial buffering (delay)’ plan, provides initial buffering for a relatively long time, preparing for degradation of service quality due to a degradation of channel situations. However, this third plan may cause an increase of an initial delay, thereby decreasing a Quality of Experience (QoE).
Therefore, a need exists for a plan that effectively ensures adaptability of a bit rate, despite degradation of channel situations, when multimedia services are provided in a dynamic wireless environment.